珠江口盆地文昌C凹陷成藏条件及勘探潜力分析

Accumulation conditions and potential analyses of Wenchang C sag in Pearl River Mouth Basin

结合地震沉积学、岩石学、地球化学、构造地质学,通过已钻井岩性、测井、有机地化等资料分析,对控制文昌C凹陷油气成藏的关键问题进行了分析。构造恢复表明凹陷内文昌组二段、三段上部2套烃源岩受后期地层剥蚀影响小。烃源岩有机质丰度高,生烃能力较强;文昌组三段储集体钻井取心砾石发育,成分主要为火山岩砾石,可见玻屑及晶屑,薄片正交光下喷出岩占整个视域40%以上,最高达73%,综合认为该段为受火山活动影响的碎屑岩储层,仍可作为较好储层。提出了"早期大断裂+厚层上覆泥岩形成的屋脊运聚体系控油"运移模式新认识,明确了文昌凹陷珠三南断裂下降盘古近系地层、上升盘新近系地层有利圈闭带,是下步勘探评价的潜力区带。

Combined with seismic sedimentology, petrology, geochemistry and tectonics, it was discussed in this paper the key factors of hydrocarbon accumulation in the Wenchang C sag through the analyses of drilling litholo-gy, well logging and geochemical data. Paleostructure restoration showed that the source rocks in the 2nd member and the upper part of the 3rd member of the Wenchang Formation experienced little effect by late denudation. The source rocks have high organic matter abundance, and have a great potential for hydrocarbon generation. There are many volcanic breccia gravels and a few shard and crystal lithics in the drilling cores from the 3rd member of the Wenchang Formation. Effusive rocks account for 40%-73% under perpendicular polarized light microscope. The 3rd member of the Wenchang Formation belongs to clastic rocks affected by volcanic activities, and is a good reservoir. A new model of hydrocarbon migration and accumulation was put forward, that was, the roof formed by early faults and overlying mudstones controlled hydrocarbon migration and accumulation. The Pa-leogene and Neogene trap belts are the most favorable exploration targets in the south of Zhu Ⅲ faults in the Wenchang C sag.